[BT8-011] Cyclomon is a LV4 black and red Digimon and a Dragonkin type. Even though it is not a Digimon with [Greymon] in its name, but it is a Dragonkin type that can be searched from BT8 Agumon, and this Digimon can be evolved from both black and red Agumon which is more flexible for the deck. On top of that, this Digimon's inheritable effect is to destroy 1 of opponent's Digimon with 2000 DP or less. It is a convenient way to destroy those annoying LV3 Digimon, such as Bokomon.
The [BT8-067] MetalGreymon, it would be better if it takes only 3 cost to digivolve into this Digimon like other LV5 Digimon, but no, it costs 4. At least it triggers "De-digivolve 1" on 1 opponent's Digimon, then delete 1 opponent's Digimon with 3000DP or less (sound good to deal with the armor release (Armor Purge)).
The most important role of Metalgreymon lands in his inheritable effect where he can grant Blackwargreymon the ability to attack the unsuspended Digimon. With the DP's boost from LV3 Agumon (ST7 Agumon and promo Agumon), Blackwargreymon can have 14000DP (without considering about which Digitama it has under its digivolution source). And again, if Blackwargreymon destroys an opponent's Digimon, he can be unsuspended once.